Demonstration of 3-dimensional wide-angle no-moving-parts laser beam steering (original) (raw)

Demonstration of 3-dimensional wide angle laser beam scanner using liquid crystals

Optics Express, 2004

Design and demonstration of a versatile liquid crystal-based scanner is shown for steering a laser beam in three dimensions. The scanner consists of a unique combination of digital and analog control polarizationbased beamforming optics resulting in both continuous and random fashion beam steering. The design features a novel device biasing method, large aperture beamforming optics, low electrical power consumption, and ultrafine as well as wide angle coarse beam steering. Demonstrations include one, two and three dimensional beam steering with a maximum of 40.92 o continuous scan, all at 1550 nm. The minimum scanner aperture is 1 cm diameter and uses a combination of ferroelectric and nematic liquid crystals in addition to Rutile crystal birefringent prisms.

Digital beam steering device based on decoupled birefringent prism de?ector and polarization rotator

2004

We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal (LC) or a solid crystal such as yttrium orthovanadate (YVO 4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2 N directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of ± 56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells.

Beam Steering Experiment with Two Cascaded Ferroelectric Liquid-Crystal Spatial Light Modulators

Applied Optics, 2004

The design, construction, and evaluation of a laser beam steerer that uses two binary ferroelectric liquid-crystal ͑FLC͒ spatial light modulators ͑SLMs͒ operated in conjunction are presented. The system is characterized by having few components and is in principle lossless. Experimentally, a throughput of ϳ20% was achieved. The simple system design was achieved because of the high tilt angle FLC material used in the SLMs, which were specifically designed and manufactured for this study. By coherently imaging the first SLM onto the second SLM, pixel by pixel, we obtained an effective four-level phase structure with a phase step of 90°. An appropriate alignment procedure is presented. The beam steering performance of the system is reported and analyzed.

Liquid Crystal Optical Phase Modulators for Beam Steering

MRS Proceedings, 2001

ABSTRACTBeamsteering using liquid crystals can be achieved with refractive or diffractive implementations. The common thread in these various structures is that the liquid crystal is employed as an optical phase modulator. Either nematic or smectic liquid crystal phases can be used to shift the phase of light and steer an optical beam. Various liquid crystal optical phase modulating schemes will be described. Examples include polarization independent and quasi-achromatic modulators. Model predictions and experimental results demonstrating the optical phase modulation and beamsteering made possible using different liquid crystal based designs will be presented.

Fast beam steering with a ferroelectric-liquid-crystal optical phased array

Applied Optics, 2009

We demonstrate fast, efficient beam steering using a single 1 × 32 analog ferroelectric liquid crystal (FLC) spatial light modulator. A high-tilt FLC material with 82°optic-axis switching provides, in a reflective-mode device with a passive quarter-wave retarder between a half-wave FLC layer and a mirror, 91% of full 0-2π phase modulation. Electronic drive based on applied charge gives 200 μs response-time analog modulation.

High resolution 2D beam steerer made from cascaded 1D liquid crystal phase gratings

Scientific Reports, 2022

Optical beam steering (BS) has multiple applications in fields like target seeking and tracking, optical tweezers, billboard displays and many others. In this work, a two-dimensional beam deflector based on blaze gratings is presented. Phase-only 1D blaze gratings have been prepared using maskless Direct Laser Writing (DLW) resulting in high-resolution structures in indium-tin oxide (ITO) coated glass wafers. The device is composed of two identical 1D liquid crystal (LC) cells cascaded orthogonally back-to-back, with a resultant active area of 1.1 × 1.1 mm 2. The 1D cells have been prepared with 144 pixels each with a 7.5 µm pitch. The total 288 pixels are driven by a custom made 12-bit Pulse Width Modulation (PWM) electronic driver, allowing for an arbitrarily high resolution. The system performance is documented, and the efficiency of the system has been tested. A maximum diagonal steering angle of ± 3.42° was achieved. Redirecting an incoming light beam to a desired direction is used in a plethora of applications where this technology is relevant such as optical tweezers 1 , optical communications 2-5 , light ranging 6-8 and augmented reality 9. Beam steerers (BSs) can be divided into two categories, depending on whether the deviation is done by a mechanical or non-mechanical control. Some mechanical approaches make use of micro-mirror or micro-lenses moved by using elements such as piezo actuators 10,11 or micro-electromechanical system 12-14. In the case of space communications, a non-mechanical system might be beneficial as no inertia is used to redirect the communication wave link, and no counterbalancing is needed. Non-mechanical methods include: electro-optics and acoustic-optics deflectors 15 and spatial light modulators (optical phase arrays that allow for addressing individual pixels) 16,17. Liquid Crystals (LCs) for non-mechanical beam deflectors exploit the electrooptical properties of this material, as it can quickly reorientate its molecules when an external electric field is applied 18,19. The simplest, positive nematic, LC is a birefringent material characterized by two refractive indices (ordinary and extraordinary) and a dielectric anisotropy with the same symmetry. When an electric field is applied to the LC the molecules will tend to align with the field vectors, resulting in an effective reorientation-switching-of the optical parameters. In LC devices the switching plane is defined by a preferred alignment direction, obtained by one of various techniques 20,21 and the applied field. Controlling the external field, it is possible to arbitrarily change the effective extraordinary index by switching the LC partially, as discussed in literature 22. Having a finite thickness means that light polarized along switching plane will experience a phase retardation depending on the switching state. LC are widely used for optical adaptative elements others than BS, for example flat tunable lenses 23-25. LC beam steerers can be considered as phase-only devices as they interact with light modifying their phase leaving other characteristics changeless 22. The objective of many studies about LC beam steerers is to improve the response-time of the device, increase the deviation angle and improve the efficiency of the process 26. Many different LC configurations for beam steering devices have been described such as Polarization Gratings (PG) 27-29 , Pancharatnam-Berry phase devices 30 , Optical Phase Arrays (OPA) 31-33 and Liquid Crystal On Silicon (LCoS) 34,35. Many different LC configurations for beam steering devices have been described such as Polarization Gratings 28,29 , Pancharatnam-Berry phase devices 30 , Optical Phase Arrays (OPAs) 31-33 and Liquid Crystal On Silicon (LCoS) 34,35 as reviewed in He et al. (2019) 18. In this review a detailed comparison of high performance OPAs 36 , PGs 37,38 , Volume Bragg gratings 39 is performed. Those deflectors in which the active area includes electronics, such as the LCoS and active-matrix thin-film transistor, cannot be adequately shielded for ionizing radiation environments. Making them unsuitable for space

Wide-angle nonmechanical beam steering using thin liquid crystal polarization gratings

2008

We introduce and demonstrate a compact, nonmechanical beam steering device based on liquid Crystal (LC) Polarization Gratings (PGs). Directional control of collimated light is essential for free-space optical communications, remote sensing, and related technologies. However, current beam steering methods often require moving parts, or are limited to small angle operation, offer low optical throughput, and are constrained by size and weight. We employ multiple layers of LCPGs to achieve wide-angle (> ±40 • ), coarse beam steering of 1550 nm light in a remarkably thin package. LCPGs can be made in switchable or polymer materials, and possess a continuous periodic birefringence profile, that renders several compelling properties (experimentally realized): ∼ 100% experimental diffraction efficiency into a single order, high polarization sensitivity, and very low scattering. Light may be controlled within and between the zero-and first-diffraction orders by the handedness of the incident light and potentially by voltage applied to the PG itself. We implement a coarse steering device with several LCPGs matched with active halfwave LC variable retarders. Here, we present the preliminary experimental results and discuss the unique capability of this wide-angle steering.